1. Preheat your oven to 350°F (175°C) and line a 12-cup muffin pan with cupcake liners.

2. In a large bowl, whisk together the all-purpose flour, caster sugar, baking powder, and fine salt.

3. In another bowl, cream the softened butter with an electric mixer until light and fluffy. Add the eggs one at a time, mixing well after each addition. Add the Greek yogurt (or sour cream), vegetable oil, and vanilla extract, mixing until fully incorporated.

4. Gradually add the dry ingredients to the wet mixture, alternating with the full cream milk, and mix until smooth.

5. Divide the batter evenly into two bowls. In one bowl, add a few drops of pink and red food gel along with the strawberry flavoring, stirring until you reach a vibrant pink color. In the other bowl, add the yellow food gel and mango flavoring, stirring until it reaches a bright yellow color.

6. Alternate spooning the strawberry and mango batters into the cupcake liners, swirling them gently with a toothpick or skewer for a marbled effect.

7. Bake the cupcakes for 18–20 minutes, or until a toothpick inserted into the center comes out clean. Let the cupcakes cool completely on a wire rack before frosting.

For the Buttercream:

1. Prepare the American or Swiss Meringue Buttercream according to your chosen recipe.

2. Divide the buttercream into two bowls. In one bowl, add pink/red food gel and strawberry flavoring to create the strawberry frosting. In the other bowl, add yellow food gel and mango flavoring to create the mango frosting.

3. Using a piping bag, pipe the frosting in alternating colors onto the cooled cupcakes. For a marbled effect, you can use a two-tone piping technique by fitting the piping bag with a two-tone frosting tip or by spooning both colors of frosting into one piping bag and swirling them together.

For the Decoration:

1. In a small pan, heat the granulated sugar over medium heat until it melts and turns golden, stirring constantly to prevent burning.

2. Once the sugar has melted and turned into caramel, carefully dip the lime wedges into the caramel and set them aside to cool on a piece of parchment paper. This will give them a sweet, crispy coating for decoration.

3. Halve the strawberries and set them aside for decoration.

4. Once the cupcakes are frosted, carefully place a caramelized lime wedge and a halved strawberry on top of each cupcake.